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Crews race to fix California dam before more rain falls

Spillway trouble

Elijah Nouvelage/Getty

CATASTROPHIC failures at a dam in California combined with heavy winter storms have forced hundreds of thousands to flee their homes. Although the level of the dam’s lake is falling fast, more rain is forecast.

On 7 February, a huge hole was found in the main concrete channel that carries overflow water from the Oroville dam to the Feather river.

Engineers diverted this water along an unpaved emergency spillway that hadn’t been used in almost 50 years – but this didn’t work. On 12 February, officials ordered over 188,000 residents of downstream towns to evacuate because the spillway was at risk of collapse.

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Unless the erosion of the spillway is dealt with, “what we’re looking at is approximately a 30-foot wall of water”, Kevin Lawson, deputy chief of the California Department of Forestry and Fire Protection, said at a press conference that night.

To lower the lake level, officials doubled the flow along the main spillway while checking it for further erosion. “That solution worked to reduce the threat,” Bill Croyle, the acting director of the California Department of Water Resources, told a press conference on 13 February. He said he was unaware of a 2005 court filing from environmental groups that warned of just such a collapse.

As New Scientist went to press, the lake level was dropping about 2.5 metres a day and water had ceased flowing over the emergency spillway.

Now the race is on to repair both spillways before it rains again.

This article appeared in print under the headline “Damning dam damage”